Emerging Insights into Brevetoxicosis in Sea Turtles

This review summarizes the current understanding of how brevetoxins, produced by Karenia brevis during harmful algal blooms, impact sea turtle health. Sea turtles may be exposed to brevetoxins through ingestion, inhalation, maternal transfer, and potentially absorption through the skin. Brevetoxins bind to voltage-gated sodium channels in the central nervous system, disrupting cellular function and inducing neurological symptoms in affected sea turtles. Moreover, the current evidence suggests a broader and longer-term impact on sea turtle health beyond what is seen during stranding events. Diagnosis relies on the detection of brevetoxins in tissues and plasma from stranded turtles. The current treatment of choice, intravenous lipid emulsion therapy, may rapidly reduce symptoms and brevetoxin concentrations, improving survival rates. Monitoring, prevention, and control strategies for harmful algal blooms are discussed. However, as the frequency and severity of blooms are expected to increase due to climate change and increased environmental pollution, continued research is needed to better understand the sublethal effects of brevetoxins on sea turtles and the impact on hatchlings, as well as the pharmacokinetic mechanisms underlying brevetoxicosis. Moreover, research into the optimization of treatments may help to protect endangered sea turtle populations in the face of this growing threat.

Blood analyte reference intervals and correlations with trace elements of immature and adult Eastern Pacific green turtles (Chelonia mydas) in coastal lagoons of Baja California Sur, México

Sea turtles can bioaccumulate high concentrations of potentially toxic contaminants. To better understand trace element effects on sea turtles' health, we established reference intervals for hematological and plasma biochemical analytes in 40 in-water, foraging immature and adult Eastern Pacific green turtles (Chelonia mydas) from two coastal lagoons in Baja California Sur, quantified whole blood concentrations of eight trace elements, and assessed their correlations. Rank-order trace element concentrations in both immature and adult turtles was zinc > selenium > nickel > arsenic > copper > cadmium > lead > manganese. Immature turtles had significantly higher copper and lower nickel and zinc concentrations. Additionally, a number of relationships between trace elements and blood analytes were identified. These data provide baseline information useful for future investigations into this population, or in other geographic regions and various life-stage classes.

Cultivating epizoic diatoms provides insights into the evolution and ecology of both epibionts and hosts

Our understanding of the importance of microbiomes on large aquatic animals—such as whales, sea turtles and manatees—has advanced considerably in recent years. The latest observations indicate that epibiotic diatom communities constitute diverse, polyphyletic, and compositionally stable assemblages that include both putatively obligate epizoic and generalist species. Here, we outline a successful approach to culture putatively obligate epizoic diatoms without their hosts. That some taxa can be cultured independently from their epizoic habitat raises several questions about the nature of the interaction between these animals and their epibionts. This insight allows us to propose further applications and research avenues in this growing area of study. Analyzing the DNA sequences of these cultured strains, we found that several unique diatom taxa have evolved independently to occupy epibiotic habitats. We created a library of reference sequence data for use in metabarcoding surveys of sea turtle and manatee microbiomes that will further facilitate the use of environmental DNA for studying host specificity in epizoic diatoms and the utility of diatoms as indicators of host ecology and health. We encourage the interdisciplinary community working with marine megafauna to consider including diatom sampling and diatom analysis into their routine practices.

Use of intravenous lipid emulsion therapy as a novel treatment for brevetoxicosis in sea turtles

The southwest coast of Florida experiences annual red tides, a type of harmful algal bloom that results from high concentrations of Karenia brevis. These dinoflagellates release lipophilic neurotoxins, known as brevetoxins, that bind to sodium channels and inhibit their inactivation, resulting in a variety of symptoms that can lead to mass sea turtle strandings. Traditional therapies for brevetoxicosis include standard and supportive care (SSC) and/or dehydration therapy; however, these treatments are slow-acting and often ineffective. Because red tide events occur annually in Florida, our objective was to test intravenous lipid emulsion (ILE) as a rapid treatment for brevetoxicosis in sea turtles and examine potential impacts on toxin clearance rates, symptom reduction, rehabilitation time, and survival rates. Sea turtles exhibiting neurological symptoms related to brevetoxicosis were brought to rehabilitation from 2018-2019. Upon admission, blood samples were collected, followed by immediate administration of 25 mg ILE/kg body mass (Intralipid® 20%) at 1 mL/min using infusion pumps. Blood samples were collected at numerous intervals post-ILE delivery and analyzed for brevetoxins using enzyme-linked immunosorbent assays. In total, nine (four subadults, one adult female, four adult males) loggerheads (Caretta caretta), five (four juvenile, one adult female) Kemp's ridleys (Lepidochelys kempii), and four juvenile green turtles (Chelonia mydas) were included in this study. We found that plasma brevetoxins declined faster compared to turtles that received only SSC. Additionally, survival rate of these patients was 94% (17/18), which is significantly higher than previous studies that used SSC and/or dehydration therapy (47%; 46/99). Nearly all symptoms were eliminated within 24-48 h, whereas using SSC, symptom elimination could take up to seven days or more. The dosage given here (25 mg/kg) was sufficient for turtles in this study, but the use of a higher dosage (50-100 mg/kg) for those animals experiencing severe symptoms may be considered. These types of fast-acting treatment plans are necessary for rehabilitation facilities that are already resource-limited. Intravenous lipid emulsion therapy has the potential to reduce rehabilitation time, save resources, and increase survival of sea turtles and other marine animals experiencing brevetoxicosis.

Evaluating prevalence of external injuries on nesting loggerhead sea turtles Caretta caretta in southeastern Florida, USA

Sea turtles face both anthropogenic and natural threats including boat strikes, fisheries, pollution, and predator attacks. Injuries from anthropogenic sources are more common than naturally caused injuries. The goal of this study was to determine prevalence and cause (e.g. boat strike, entanglement, hook, shark bite) of injuries on nesting loggerhead sea turtles Caretta caretta on Juno and Jupiter beaches, Florida, USA. During the 2019 and 2020 nesting seasons, 450 loggerhead females were examined for external injuries. Injuries were categorized by anatomic location, condition, and cause. We found that 24% of loggerheads had at least 1 injury. Of the 111 injuries found on 107 nesting females, 88% were healed, 9% were partially healed with some scarred tissue, and 3% were fresh injuries. Most injuries (55%) were lateral injuries on the carapace or appendages. We were able to attribute 60 injuries to a specific cause. Boat strikes accounted for 75% of the 60 injuries, shark bites accounted for 15%, fishing hooks accounted for 7%, and entanglements accounted for the remaining 3%. This study provides new insight into the prevalence of anthropogenic injuries relative to natural injuries in loggerhead sea turtles nesting in the most densely nested beach in the Western Hemisphere and can be used to improve conservation management plans through implementation of fishing and/or boating restrictions in the nesting and foraging areas most commonly frequented by sea turtles.

Global COVID-19 lockdown highlights humans as both threats and custodians of the environment

The global lockdown to mitigate COVID-19 pandemic health risks has altered human interactions with nature. Here, we report immediate impacts of changes in human activities on wildlife and environmental threats during the early lockdown months of 2020, based on 877 qualitative reports and 332 quantitative assessments from 89 different studies. Hundreds of reports of unusual species observations from around the world suggest that animals quickly responded to the reductions in human presence. However, negative effects of lockdown on conservation also emerged, as confinement resulted in some park officials being unable to perform conservation, restoration and enforcement tasks, resulting in local increases in illegal activities such as hunting. Overall, there is a complex mixture of positive and negative effects of the pandemic lockdown on nature, all of which have the potential to lead to cascading responses which in turn impact wildlife and nature conservation. While the net effect of the lockdown will need to be assessed over years as data becomes available and persistent effects emerge, immediate responses were detected across the world. Thus, initial qualitative and quantitative data arising from this serendipitous global quasi-experimental perturbation highlights the dual role that humans play in threatening and protecting species and ecosystems. Pathways to favorably tilt this delicate balance include reducing impacts and increasing conservation effectiveness.

Fibropapillomatosis and Chelonid Alphaherpesvirus 5 Infection in Kemp's Ridley Sea Turtles (Lepidochelys kempii)

Simple Summary

The Kemp’s ridley sea turtle is an endangered species that is susceptible to a tumor disease called fibropapillomatosis (FP) and its associated virus, chelonid alphaherpesvirus 5 (ChHV5). The goal of our study was to describe FP in Kemp’s ridley turtles, including estimated disease prevalence and pathologyg, and case demographics and outcomes, to better understand the risk posed by FP to Kemp’s ridley population recovery. During 2006–2020, we identified 22 cases of Kemp’s ridley turtles with FP, including 12 adult turtles, a reproductively valuable age class. Molecular diagnostics were used to identify ChHV5 DNA in blood (7.8%) and tumor (91.7%) samples collected from free-ranging Kemp’s ridley turtles. Genomic sequencing was conducted to identify ChHV5 variants in tumor samples collected from Kemp’s ridley turtles with FP. Along with case data, phylogenetic analysis of resultant sequences suggests increasing, spatiotemporal spread of ChHV5 infections and FP among Kemp’s ridley turtles in coastal areas, including the Gulf of Mexico and the southwestern Atlantic Ocean, where they share habitat with green sea turtles (in which FP is enzootic). This is concerning because FP has an uncertain pathogenesis, is potentially related to anthropogenic environmental degradation, and can cause suffering and/or death in severely afflicted turtles.

Abstract

Fibropapillomatosis (FP), a debilitating, infectious neoplastic disease, is rarely reported in endangered Kemp’s ridley sea turtles (Lepidochelys kempii). With this study, we describe FP and the associated chelonid alphaherpesvirus 5 (ChHV5) in Kemp’s ridley turtles encountered in the United States during 2006–2020. Analysis of 22 case reports of Kemp’s ridley turtles with FP revealed that while the disease was mild in most cases, 54.5% were adult turtles, a reproductively valuable age class whose survival is a priority for population recovery. Of 51 blood samples from tumor-free turtles and 12 tumor samples from turtles with FP, 7.8% and 91.7%, respectively, tested positive for ChHV5 DNA via quantitative polymerase chain reaction (qPCR). Viral genome shotgun sequencing and phylogenetic analysis of six tumor samples show that ChHV5 sequences in Kemp’s ridley turtles encountered in the Gulf of Mexico and northwestern Atlantic cluster with ChHV5 sequences identified in green (Chelonia mydas) and loggerhead (Caretta caretta) sea turtles from Hawaii, the southwestern Atlantic Ocean, and the Caribbean. Results suggest an interspecific, spatiotemporal spread of FP among Kemp’s ridley turtles in regions where the disease is enzootic. Although FP is currently uncommon in this species, it remains a health concern due to its uncertain pathogenesis and potential relationship with habitat degradation.

Mercury offloading in gametes and potential adverse effects of high mercury concentrations in blood and tissues of Atlantic Goliath Grouper Epinephelus itajara in the southeastern United States

Mercury (Hg) is a ubiquitous and non-essential heavy metal that is highly toxic to aquatic organisms. Few studies examine Hg and its effects on wild fish populations. Here, we investigated the potential effects of Hg exposure on a large and long-lived marine species of conservation concern, the vulnerable Atlantic Goliath Grouper Epinephelus itajara. Our objectives were (1) to measure Hg (methyl-Hg; and total Hg = combined methyl-Hg and inorganic-Hg) concentrations in whole blood (WB) and gametes (eggs and sperm); (2) to investigate the relationships between Hg concentrations in muscle and liver with WB and gametes; (3) to investigate the relationships between Hg concentrations in liver, muscle, and WB with hematological and plasma biochemical analytes; and (4) to investigate the relationship between liver Hg and pigmented macrophage aggregates in liver tissue sections. We found several lines of evidence for potential adverse effects on Goliath Grouper health and reproduction by high Hg concentrations in liver, muscle, WB, and gametes, including (1) Hg concentrations in all tissues and gametes were well above observable ranges of marine and freshwater fishes from experimental exposure studies; (2) gamete Hg concentrations were among the highest recorded in wild fishes, with seasonal patterns suggesting females offload significant amounts of Hg into their eggs during the spawning season; (3) Methyl-Hg was highest in muscle, followed by sperm, liver, eggs, and WB; (4) there were significant correlations between liver, muscle, and WB Hg concentrations with various blood analytes; (5) vitellogenin positively correlated with female liver methyl-Hg concentrations, and was abnormally high in males, suggesting direct endocrine effects; and (6) liver total Hg positively correlated with pigmented macrophage aggregate count and percent area. This work will help guide future research examining the potential adverse effects of Hg and its role as an additional stressor on wild fish populations.

Two heads are not always better than one: Craniofacial and axial bifurcation in cheloniid embryos and hatchlings (Chelonia mydas and Caretta caretta)

Morphological data on craniofacial and axial bifurcation in sea turtles is not well documented in the literature. Here, we use micro-computed tomography (μ-CT) imaging to describe the body, skull, and vertebral morphology in axially-bifurcated cheloniid sea turtle embryos and hatchlings (Chelonia mydas and Caretta caretta) from south Florida beaches. We describe three types of craniofacial and axial bifurcations: bifacial, bicephalic, and bicephalic with biaxial duplication ranging from facial bones to the sacrum. We predicted smaller body dimensions in bifacial and bicephalic embryos and hatchlings compared with their normal counterparts. In addition, we hypothesized that bicephalic individuals would have greater rostral deviation angles than bifacial animals, and that vertebral dimensions would vary between the control and anomalous embryos and hatchlings. Among hatchlings (developmental Stage 31), we found that maximum curved carapace length and curved carapace width were greatest in the control specimens when compared with the anomalous specimens. Overall, we found that rostral deviations were smaller in bifacial animals compared with their bicephalic counterparts. Right and left rostral deviations were symmetrical or nearly symmetrical in all bifacial and bicephalic specimens. Among C. caretta, we found that bicephalic animals had greater standardized vertebral measurements than their bifacial conspecifics. In bifacial animals, bifurcation extended to either the frontal or parietal skull bones, while duplication extended to C5 vertebrae and T8 vertebrae in bicephalic animals. This study provides an in-depth description of anatomical alterations associated with these abnormalities. Prognosis of these organisms is poor; however, understanding the prevalence of these malformations can allow for better assessments of population health, as numerous environmental factors are known to lead to these changes.

Comprehensive health assessment and blood analyte reference intervals of gopher tortoises (Gopherus polyphemus) in southeastern FL, USA

The gopher tortoise (Gopherus polyphemus), a keystone species, is declining throughout its geographic range. Lack of knowledge with respect to the potential infectious diseases present within wild populations creates a dilemma for wildlife biologists, conservationists and public policy makers. The objective of this study was to conduct a health assessment of two previously unstudied gopher tortoise aggregations located at two sites in southeastern FL. Samples were collected from 91 tortoises (48 adults, 35 juveniles, 8 hatchlings) captured at Florida Atlantic University's Harbor Branch Oceanographic Institute, in Fort Pierce, FL, USA in 2019, and Loggerhead Park in Juno Beach, FL, USA, during 2018-2019. Samples of blood, nasal swabs and oral/cloacal swabs were analyzed for hematology, plasma protein electrophoretic profiles and infectious disease testing including Mycoplasma spp. serology and polymerase chain reaction (PCR) assays for Ranavirus, Herpesvirus and Anaplasma spp. Hematological and plasma protein electrophoresis reference intervals are presented for adult and juvenile tortoises from both sites combined. Clinical signs consistent with upper respiratory tract disease (URTD) were observed in 18/91 (20%) tortoises, and antibodies to Mycoplasma agassizii were detected in 33/77 (42.9%) tortoises. Adult tortoises were significantly more likely than juveniles to have URTD clinical signs, and statistically significant, positive relationships were observed between the presence of antibodies to Mycoplasma spp. and carapace length, packed cell volume and plasma globulin concentrations. Anaplasma spp. inclusions were observed in 8/82 (10%) tortoises, but PCR detected Anaplasma sp. in 21/83 (25%) tortoises. Herpesvirus and Ranavirus were not detected in any blood or swab samples. This work contributes important baseline information on the health of gopher tortoises toward the southern end of the species' range.

Comparison of 2 glucose analytical methodologies in immature Kemp's ridley sea turtles: dry chemistry of plasma versus point-of-care glucometer analysis of whole blood

Blood glucose measurements provide important diagnostic information regarding stress, disease, and nutritional status. Glucose analytical methodologies include dry chemistry analysis (DCA) of plasma and point-of-care (POC) glucometer analysis of whole blood; however, these 2 methods differ in cost, required sample volume, and processing time. Because POC glucometers use built-in equations based on features of mammalian blood to convert whole blood measurements to plasma equivalent units, obtained glucose data must be compared and validated using gold-standard chemistry analytical methodology in reptiles. For in-water, trawl-captured, immature Kemp's ridley sea turtles (Lepidochelys kempii) from Georgia, USA, we observed significant, positive agreement between the 2 glucose determination methods; however, the glucometer overestimated glucose concentrations by 1.4 mmol/L on average in comparison to DCA and produced a wider range of results. The discordance of these results suggests that POC glucometer glucose data should be interpreted in the context of methodology- and brand-specific reference intervals along with concurrent packed cell volume data.

Plasma proteomics of green turtles (Chelonia mydas) reveals pathway shifts and potential biomarker candidates associated with health and disease

Evaluating sea turtle health can be challenging due to an incomplete understanding of pathophysiologic responses in these species. Proteome characterization of clinical plasma samples can provide insights into disease progression and prospective biomarker targets. A TMT-10-plex-LC-MS/MS platform was used to characterize the plasma proteome of five, juvenile, green turtles (Chelonia mydas) and compare qualitative and quantitative protein changes during moribund and recovered states. The 10 plasma samples yielded a total of 670 unique proteins. Using ≥1.2-fold change in protein abundance as a benchmark for physiologic upregulation or downregulation, 233 (34.8%) were differentially regulated in at least one turtle between moribund and recovered states. Forty-six proteins (6.9%) were differentially regulated in all five turtles with two proteins (0.3%) demonstrating a statistically significant change. A principle component analysis showed protein abundance loosely clustered between moribund samples or recovered samples and for turtles that presented with trauma (n = 3) or as intestinal floaters (n = 2). Gene Ontology terms demonstrated that moribund samples were represented by a higher number of proteins associated with blood coagulation, adaptive immune responses and acute phase response, while recovered turtle samples included a relatively higher number of proteins associated with metabolic processes and response to nutrients. Abundance levels of 48 proteins (7.2%) in moribund samples significantly correlated with total protein, albumin and/or globulin levels quantified by biochemical analysis. Differentially regulated proteins identified with immunologic and physiologic functions are discussed for their possible role in the green turtle pathophysiologic response and for their potential use as diagnostic biomarkers. These findings enhance our ability to interpret sea turtle health and further progress conservation, research and rehabilitation programs for these ecologically important species.

The Iconic Atlantic Goliath Grouper (Epinephelus itajara): A Comprehensive Assessment of Health Indices in the Southeastern United States Population

The Atlantic Goliath Grouper (Epinephelus itajara) population has rebounded from near extinction to an international status as vulnerable due in part to regional species recovery efforts. The southeastern US population has been recovering with the main spawning locations off the coasts of Florida. Despite their economic importance to the catch-and-release fishery and the dive industry, and their ecological importance as ecosystem engineers resulting in positive impacts on reefs and species richness, baseline health assessment information is very limited in this species to date. The objectives of this study were to: (1) establish reference intervals for hematological and plasma biochemical analytes, and report immune function, oxidative stress, and vitellogenin in mature males and females; (2) evaluate total length, age, and sex in relation to blood analytes in juvenile and mature fish; (3) assess analytes across sampled months in mature male and female fish; and (4) describe the typical light microscopy findings in liver and gill biopsies, including quantitative assessment of pigmented macrophage aggregates. Health indices are reported as reference intervals when applicable, or otherwise descriptively. Blood analyte correlations with length and age, sex differences, and comparisons across months provided relevant physiological considerations, including differences in protein/energy metabolism, tissue growth, sexual maturation, active reproduction, and antigenic stimulation. Liver histology identified changes associated with life stage, active reproduction, or of subclinically to clinically insignificant infectious and/or inflammatory processes. Hepatocellular vacuolation and pigmented macrophage aggregates were prominent. Pigmented macrophage aggregates correlated with total length, presumably from continuous antigenic stimulation and/or metabolic changes as fish grow. Gill histological findings were subtle. The data presented herein provide an essential baseline assessment of a suite of health variables in an iconic marine teleost species, serves as a springboard for future studies relevant to conservation physiology, and allows for population-level applications for conservation management and policy.

Comprehensive health assessment of green turtles Chelonia mydas nesting in southeastern Florida, USA

Important indicators of population health needed for large-scale sea turtle population recovery efforts include demographics, disease and mortality trends, condition indices, and baseline blood data. With this comprehensive health assessment of adult female green sea turtles Chelonia mydas nesting on Juno Beach, Florida, USA, we (1) established comprehensive baseline health indices; (2) identified individuals with evidence of infection by chelonid alphaherpesviruses 5 and 6 (ChHV5, ChHV6), which are implicated in fibropapillomatosis and respiratory and skin disease, respectively; and (3) compared measured health indices between turtles that did versus those that did not test positive for ChHV5 and/or ChHV6. All 60 turtles included in the study were in good body condition with no external fibropapillomatosis tumors. Hematological and biochemical reference intervals were established. Via quantitative PCR (qPCR), 5/60 turtles (8%) tested positive for ChHV5, and all turtles were negative for ChHV6. Of 41 turtles tested for antibodies to ChHV5 and ChHV6, 29% and 15% tested positive, respectively, and 10% tested positive for antibodies to both viruses. Notably, there were no statistically significant differences between health variables for nesting turtles that tested positive for ChHV5 DNA versus those that tested negative; and also no differences between turtles that tested positive for ChHV5 or ChHV6 antibodies and those that did not. This suggests that these viruses are enzootically stable in Florida’s adult green turtles. This study provides a health profile of nesting green turtles in southeastern Florida applicable to temporal and spatial investigations of this and other populations.

Morphological variation in leatherback (Dermochelys coriacea) hatchlings at Sandy Point National Wildlife Refuge, US Virgin Islands

Understanding species’ mating systems provides important information about their ecology, life history, and behavior. Direct observations of mating behaviors can be challenging, but molecular techniques can reveal information about mating systems and paternal identity in difficult-to-observe species such as sea turtles. Genetic markers can be used to assess the paternity of a clutch and to assign hatchlings to a father. Leatherback turtles Dermochelys coriacea sometimes mate with multiple individuals, resulting in clutches with mixed paternity; however, the effects of multiple paternity on hatchling quality are unclear. Leatherback hatchlings at Sandy Point National Wildlife Refuge, St. Croix, US Virgin Islands, exhibit visible variation in individual body size, sometimes within the same clutch. We collected morphometrics and tissue samples from hatchlings across multiple nesting seasons (2009, 2012, 2013, 2015, and 2016) and found that hatchlings exhibited small but statistically significant differences in morphometrics between years. We used maternal and hatchling microsatellite genotypes to reconstruct paternal genotypes, assigning fathers to each hatchling. We found multiple paternity in 5 of 17 clutches analyzed and compared differences in morphometrics between full-siblings with differences between half-siblings. We found no significant differences between morphometrics of hatchlings from the same mother but different fathers. We compared within-clutch variances in morphometrics for clutches with and without multiple paternity and found no significant difference in morphological variation between them. Therefore, we could not attribute differences in hatchling size within a clutch to paternal contribution. Understanding other factors affecting hatchling morphology, and other possible fitness metrics, may reveal insights into the benefits, or lack thereof, of polyandry in sea turtles.

Impact of the fire ant pesticide AMDRO on loggerhead turtle nest productivity and seafinding orientation

Invasive fire ants prey on a variety of organisms in the southeastern USA, including the pipped eggs and hatchlings within sea turtle nests. The granular fire ant bait AMDRO® (active ingredient hydramethylnon) is currently used at some rookeries to protect nests, but no studies have been conducted to determine if the pesticide negatively impacts the eggs or the hatchlings. We examined the pesticide’s effect on loggerhead (Caretta caretta) nests at Juno Beach, Florida, USA, specifically targeting how exposure affected hatching success, hatchling emergence success, and the ability of the turtles to orient visually from the nest to the sea. Pesticide granules were placed within a 30 cm diameter circle on the sand directly above the nest during the final 5-10 days of incubation, representative of its typical application at nesting beaches. Cornmeal granules in soybean oil and untreated natural nests served as controls. AMDRO had no significant effect on hatching success or emergence success, nor did it result in any deficiencies in hatchling orientation accuracy. However, the pesticide and cornmeal control attracted other predators (Atlantic ghost crabs and avian species), in addition to fire ants, to the nest site, thus revealing the nest’s location and potentially increasing its vulnerability. Consequently, we suggest that its usage may not be beneficial at sites where predators other than ants are especially abundant.

Pre-/analytical factors affecting whole blood and plasma glucose concentrations in loggerhead sea turtles (Caretta caretta)

Blood glucose is vital for many physiological pathways and can be quantified by clinical chemistry analyzers and in-house point-of-care (POC) devices. Pre-analytical and analytical factors can influence blood glucose measurements. This project aimed to investigate pre-analytical factors on whole blood and plasma glucose measurements in loggerhead sea turtles (Caretta caretta) by evaluating the effects of storage (refrigeration) up to 48h after sampling and of packed cell volume (PCV) on whole blood glucose analysis by POC glucometer (time series n = 13); and by evaluating the effects of storage (room temperature and refrigeration) on plasma glucose concentrations using a dry slide chemistry analyzer (DCA) at various conditions: immediate processing and delayed plasma separation from erythrocytes at 24h and 48h (time series n = 14). The POC glucometer had overall strong agreement with the DCA (CCC = 0.76, r = 0.84, C_b = 0.90), but consistently overestimated glucose concentrations (mean difference: +0.4 mmol/L). The POC glucometer results decreased significantly over time, resulting in a substantial decline within the first 2h (0.41±0.47 mmol/L; 8±9%) that could potentially alter clinical decisions, thereby highlighting the need for immediate analysis using this method. The effects of PCV on glucose could not be assessed, as the statistical significance was associated with one outlier. Storage method significantly affected plasma glucose measurements using DCA, with room temperature samples resulting in rapid decreases of 3.57±0.89 mmol/L (77±9%) over the first 48h, while refrigerated samples provided consistent plasma glucose results over the same time period (decrease of 0.26±0.23 mmol/L; 6±5%). The results from this study provide new insights into optimal blood sample handling and processing for glucose analysis in sea turtles, show the suitability of the POC glucometer as a rapid diagnostic test, and confirm the reliability of plasma glucose measurements using refrigeration. These findings emphasize the need to consider pre-/analytical factors when interpreting blood glucose results from loggerhead sea turtles.

Heat, health and hatchlings: associations of in situ nest temperatures with morphological and physiological characteristics of loggerhead sea turtle hatchlings from Florida

Incubation temperatures, in addition to an embryo's genetic makeup, are critical in many aspects of adequate sea turtle embryonic development. The effects of high and low incubation temperatures on hatchling quality have been previously examined; however, many of these studies were conducted on relocated or laboratory-reared nests, which do not accurately reflect natural nest temperature fluctuations. To observe the impacts of varying in situ incubation temperatures on loggerhead sea turtle (Caretta caretta) hatchling morphology, various health variables and locomotor performance, temperature data loggers were deployed in 15 loggerhead nests on Juno Beach, Florida, between May and July 2018. Over the course of the study period, 10 morphological traits were measured, blood analytes and heart rate were assessed for the establishment of reference intervals and the self-righting response in seawater was evaluated. Warmer months were associated with smaller body size and higher body condition index, larger umbilical scar size, slower righting time, lower heart rates and higher packed cell volume, hemoglobin, total solids, total white blood cell count, absolute heterophils and absolute basophils. These findings provide evidence that higher in situ incubation temperatures have the potential to adversely affect hatchlings from warmer nests due to increased risk of predation from smaller body sizes, decreased physical responses and overall fitness, altered hemodynamic balance (e.g. dehydration) and potential inflammation and/or stress. With rising temperatures, we predict sea turtle hatchlings may have increasing risks of developing suboptimal physiological features affecting overall fitness and ultimately survival. These results demonstrate that rising environmental temperatures can negatively impact sea turtle hatchlings, thus representing additional stress on sea turtle populations and contributing to our understanding of potential pathophysiological effects of climate change on the delicate life-stage class of the sea turtle hatchling. This information will be useful for formulating effective future sea turtle management plans.

Blood analytes of immature Kemp's ridley sea turtles (Lepidochelys kempii) from Georgia, USA: reference intervals and body size correlations

Health assessments of wildlife species are becoming increasingly important in an ever-changing environment. Kemp's ridley sea turtles (Lepidochelys kempii; hereafter, Kemp's ridleys) are critically endangered and incur several on-going threats to their population recovery; therefore, it is imperative to advance the understanding of baseline blood analyte data as a diagnostic and monitoring tool. For in-water, trawl-captured, immature Kemp's ridleys (minimum N = 31) from Georgia, USA, the objectives of this study were to (1) establish reference intervals (RIs) for packed cell volume (PCV) and 27 plasma biochemistry analytes and (2) determine length-specific relationships in blood analytes. We observed significant positive correlations between minimum straight carapace length and PCV, amylase, calcium:phosphorus ratio, cholesterol, magnesium, triglycerides, total solids, total protein and all protein fractions (e.g. alpha-, beta- and gamma-globulins); aspartate aminotransferase and chloride showed significant negative relationships. These results suggest that certain blood analytes in Kemp's ridleys change as these animals grow, presumptively due to somatic growth and dietary shifts. The information presented herein, in due consideration of capture technique that may have impacted glucose and potassium concentrations, represents the first report of blood analyte RIs for Kemp's ridley sea turtles established by guidelines of the American Society for Veterinary Clinical Pathology and will have direct applications for stranded individuals in rehabilitative care and for future investigations into the health status of wild individuals from this population.

Tumor re-growth, case outcome, and tumor scoring systems in rehabilitated green turtles with fibropapillomatosis

Fibropapillomatosis (FP) is an infectious, neoplastic disease of major concern in sea turtle rehabilitation facilities. Rehabilitating sea turtles that undergo tumor removal surgery often have tumor regrowth and may experience mortality. We evaluated tumor score, removal, and regrowth in rehabilitating green sea turtles with FP in 4 rehabilitation facilities in the southeastern USA during 2009-2017. Of 756 cases, 312 (41%) underwent tumor removal surgery, 155 (50%) of those had tumor regrowth within an average of 46 ± 45 d, and 85 (27%) had multiple (>1) regrowth events. Of 756 turtles with FP, 563 (75%) did not survive after admission into a rehabilitation facility, including 283 (37%) that were euthanized and 280 that died without euthanasia (37%), and 193 survived, including 186 (25%) released and 7 (1%) placed in permanent captive care. Tumor removal surgery increased the odds of tumor regrowth but also enhanced survivorship, whereas tumor regrowth was not a significant predictor of case outcome. Three FP tumor scoring systems were used to assign tumor scores to 449 cases, and differing results emphasize that tumor scoring systems should be applied to the situations and/or location(s) for which they were intended. FP tumor score was not a significant predictor for the event or extent of FP tumor regrowth after surgical excision. Under current rehabilitation regimes, outcomes of rehabilitation for tumored turtles have a low probability of success. The results of this study may be used to help guide clinical decision-making and determine prognoses for rehabilitating sea turtles with FP.

Plasma chemistry in nesting leatherback sea turtles (Dermochelys coriacea) from Florida: Understanding the importance of sample hemolysis effects on blood analytes

Plasma chemistry is widely used in diagnostic and research settings in sea turtles. However, plasma discolorations such as hemolysis are often not considered in data interpretation. The objectives of this study were to (1) evaluate the effects of moderate hemolysis on plasma electrolytes, minerals, and proteins using dry chemistry analysis (DCA) and protein electrophoresis from nesting leatherback sea turtles (Dermochelys coriacea) from Florida and to (2) establish blood analyte reference intervals. Twenty-six plasma samples with absence of hemolysis were selected and sub-divided into one non-hemolytic aliquot and an aliquot that was experimentally manipulated to mimic moderate hemolysis. Plasma samples were analyzed for hemoglobin using a handheld photometer; sodium, potassium, chloride, magnesium, calcium, phosphorus, and total protein using DCA; and protein electrophoresis. Packed cell volume and hemoglobin were measured in corresponding whole blood samples. Reference intervals were established. All analytes except calcium and pre-albumin were significantly higher and the calcium:phosphorus and albumin:globulin ratios were significantly lower in hemolytic plasma compared to non-hemolytic plasma. Alpha2-globulins and potassium were the analytes most impacted by hemolysis, averaging 3.3- and 2.0-fold higher in hemolyzed samples, respectively, indicating that (1) hemoglobin migrates into the alpha2-globulin region in this species and (2) notable intracellular potassium is released into plasma with hemolysis. Attempted conversion factors for compensation of hemolysis were considered inaccurate for 4 of 16 analytes due to non-significant regression lines. We also report that PCV provides an estimate of hemoglobin (g/L) using the formula: (2.59 × PCV) + 24.59. Given the spurious effects of hemolysis, the degree of this artifact should be reported with biochemistry data, and samples with moderate to severe hemolysis should be excluded from datasets when interpreting electrolyte, mineral, and protein results. This will ensure accurate data interpretation for individual turtles in rehabilitation or research settings and population-level data relevant to conservation-focused projects.

Evidence of accumulation and elimination of inorganic contaminants from the lachrymal salt glands of leatherback sea turtles (Dermochelys coriacea)

Plasma osmolalities of marine vertebrates are generally lower than the surrounding medium; therefore, marine organisms must cope with the osmoregulatory challenges of life in a salty environment. The salt glands serve to maintain osmotic and ionic homeostasis in a number of lower marine vertebrates. One marine reptile, the leatherback sea turtle (Dermochelys coriacea), ingests excessive amounts of salts due to their diet of gelatinous zooplankton. Outside of the normal osmoregulatory function of the salt gland, little research has been conducted on contaminant accumulation and excretion in this organ. Here, we established arsenic, cadmium, lead, mercury, and selenium concentrations in red blood cells (RBCs) and salt gland secretions (SGSs) of nesting leatherbacks. We also collected salt glands from different life stage classes of dead stranded leatherbacks from the western Atlantic Ocean to determine if inorganic contaminants accumulate in this organ. Using non-metric multidimensional scaling and regression analyses, we determined that RBC and SGS inorganic contaminant concentrations were not correlated. Additionally, RBCs showed significantly higher concentrations of these contaminants in comparison to SGSs, likely due to the affinity of inorganic contaminants for the heme group of RBCs. Lastly, we found that salt gland cadmium and mercury concentrations tended to increase with increasing curved carapace length (CCL) in stranded leatherbacks. Our results indicate that different physiological mechanisms determine the distribution of inorganic contaminants in blood and SGSs. Increases in salt gland contaminant concentrations with increasing CCL suggest this organ as a potential target for accumulation.

Mercury and selenium concentrations in Scyphozoan jellyfishes and pyrosomes from Monterey Bay National Marine Sanctuary

Gelatinous zooplankton including jellyfishes, pyrosomes, and salps serve as important prey items for a number of marine species; however, relatively few studies have examined contaminant concentrations in these animals. Scyphozoans (Aurelia sp., Chrysaora colorata, C. fuscescens, and Phacellophora camtschatica) and Thaliaceans (Pyrosoma sp.) were collected from 2009 to 2011 from Monterey Bay National Marine Sanctuary and analyzed for total mercury and selenium concentrations. In general, mercury (0.0001-0.0016 μg/g wet weight) and selenium (0.009-0.304 μg/g wet weight) concentrations of the sampled organisms were low; however, the two Pyrosoma sp. had total mercury and selenium concentrations that were one order of magnitude higher than the Scyphozoans. There was a significant positive relationship between mercury and selenium concentrations in jellyfishes and pyrosomes, suggesting a potential detoxification mechanism in these lower trophic level organisms. This study provides evidence that trophic transfer of mercury and selenium likely occurs through ingestion of gelatinous prey.

Blood analytes of oceanic-juvenile loggerhead sea turtles (Caretta caretta) from Azorean waters: reference intervals, size-relevant correlations and comparisons to neritic loggerheads from western Atlantic coastal waters

Blood analyte reference intervals are scarce for immature life stages of the loggerhead sea turtle (Caretta caretta). The objectives of this study were to (1) document reference intervals of packed cell volume (PCV) and 20 plasma chemistry analytes from wild oceanic-juvenile stage loggerhead turtles from Azorean waters, (2) investigate correlations with body size (minimum straight carapace length: SCL_min) and (3) compare plasma chemistry data to those from older, larger neritic juveniles (<80 cm SCL_min) and adult loggerheads (≥80 cm SCL_min) that have recruited to the West Atlantic in waters around Cape Canaveral, Florida. Twenty-eight Azorean loggerhead turtles with SCL_min of 17.6-60.0 cm (mean 34.9 ± 12.1 cm) were captured, sampled and immediately released. Reference intervals are reported. There were several biologically relevant correlations of blood analytes with SCL_min: positive correlations of PCV, proteins and triglycerides with SCL_min indicated somatic growth, increasing diving activity and/or diet; negative correlations of tissue enzymes with SCL_min suggested faster growth at smaller turtle size, while negative correlations of electrolytes with SCL_min indicated differences in diet, environmental conditions and/or osmoregulation unique to the geographic location. Comparisons of loggerhead turtles from the Azores (i.e. oceanic) and Cape Canaveral (i.e. neritic) identified significant differences regarding diet, somatic growth, and/or environment: in Azorean turtles, albumin, triglycerides and bilirubin increased with SCL_min, while alkaline phosphatase, lactate dehydrogenase and sodium decreased. In larger neritic Cape Canaveral turtles, aspartate aminotransferase increased with SCL_min, while the albumin:globulin ratio, phosphorus and cholesterol decreased. These differences suggest unique physiological disparities between life stage development and migration, reflecting biological and habitat differences between the two populations. This information presents biologically important data that is applicable to stranded individual turtles and to the population level, a tool for the development of conservation strategies, and a baseline for future temporal and spatial investigations of the Azorean loggerhead sea turtle population.

Potential effects of brevetoxins and toxic elements on various health variables in Kemp's ridley (Lepidochelys kempii) and green (Chelonia mydas) sea turtles after a red tide bloom event

Natural biotoxins and anthropogenic toxicants pose a significant risk to sea turtle health. Documented effects of contaminants include potential disease progression and adverse impacts on development, immune function, and survival in these imperiled species. The shallow seagrass habitats of Florida's northwest coast (Big Bend) serve as an important developmental habitat for Kemp's ridley (Lepidochelys kempii) and green (Chelonia mydas) sea turtles; however, few studies have been conducted in this area. Our objectives were (1) to evaluate plasma analytes (mass, minimum straight carapace length, body condition index [BCI], fibropapilloma tumor score, lysozyme, superoxide dismutase, reactive oxygen/nitrogen species, plasma protein electrophoresis, cholesterol, and total solids) in Kemp's ridleys and green turtles and their correlation to brevetoxins that were released from a red tide bloom event from July-October 2014 in the Gulf of Mexico near Florida's Big Bend, and (2) to analyze red blood cells in Kemp's ridleys and green turtles for toxic elements (arsenic, cadmium, lead, mercury, selenium, thallium) with correlation to the measured plasma analytes. Positive correlations were observed between brevetoxins and α₂-globulins in Kemp's ridleys and α₂- and γ-globulins in green turtles, indicating potential immunostimulation. Arsenic, cadmium, and lead positively correlated with superoxide dismutase in Kemp's ridleys, suggesting oxidative stress. Lead and mercury in green turtles negatively correlated with BCI, while mercury positively correlated with total tumor score of green turtles afflicted with fibropapillomatosis, suggesting a possible association with mercury and increased tumor growth. The total tumor score of green turtles positively correlated with total protein, total globulins, α₂-globulins, and γ-globulins, further suggesting inflammation and immunomodulation as a result of fibropapillomatosis. Lastly, brevetoxin concentrations were positively related to tumor score, indicating potential tumor promotion by brevetoxin. These results signify that brevetoxins and toxic elements elicit various negative effects on sea turtle health, including immune function, oxidative stress, and possibly disease progression.

Toxic elements and associations with hematology, plasma biochemistry, and protein electrophoresis in nesting loggerhead sea turtles (Caretta caretta) from Casey Key, Florida

Toxic elements (arsenic, cadmium, lead, mercury, selenium, thallium) are a group of contaminants that are known to elicit developmental, reproductive, general health, and immune system effects in reptiles, even at low concentrations. Reptiles, including marine turtles, are susceptible to accumulation of toxic elements due to their long life span, low metabolic rate, and highly efficient conversion of prey into biomass. The objectives of this study were to (1) document concentrations of arsenic, cadmium, lead, mercury, selenium, and thallium in whole blood and keratin from nesting loggerhead sea turtles (Caretta caretta) from Casey Key, Florida and document correlations thereof and (2) correlate whole blood toxic element concentrations to various hematological and plasma biochemistry analytes. Baselines for various hematological and plasma analytes and toxic elements in whole blood and keratin (i.e., scute) in nesting loggerheads are documented. Various correlations between the toxic elements and hematological and plasma biochemistry analytes were identified; however, the most intriguing were negative correlations between arsenic, cadmium, lead, and selenium with and α- and γ-globulins. Although various extrinsic and intrinsic variables such as dietary and feeding changes in nesting loggerheads need to be considered, this finding may suggest a link to altered humoral immunity. This study documents a suite of health variables of nesting loggerheads in correlation to contaminants and identifies the potential of toxic elements to impact the overall health of nesting turtles, thus presenting important implications for the conservation and management of this species.

Maternal transfer and sublethal immune system effects of brevetoxin exposure in nesting loggerhead sea turtles (Caretta caretta) from western Florida

Blooms of Karenia brevis (also called red tides) occur almost annually in the Gulf of Mexico. The health effects of the neurotoxins (i.e., brevetoxins) produced by this toxic dinoflagellate on marine turtles are poorly understood. Florida's Gulf Coast represents an important foraging and nesting area for a number of marine turtle species. Most studies investigating brevetoxin exposure in marine turtles thus far focus on dead and/or stranded individuals and rarely examine the effects in apparently "healthy" free-ranging individuals. From May-July 2014, one year after the last red tide bloom, we collected blood from nesting loggerhead sea turtles (Caretta caretta) on Casey Key, Florida USA. These organisms show both strong nesting and foraging site fidelity. The plasma was analyzed for brevetoxin concentrations in addition to a number of health and immune-related parameters in an effort to establish sublethal effects of this toxin. Lastly, from July-September 2014, we collected unhatched eggs and liver and yolk sacs from dead-in-nest hatchlings from nests laid by the sampled females and tested these samples for brevetoxin concentrations to determine maternal transfer and effects on reproductive success. Using a competitive enzyme-linked immunosorbent assay (ELISA), all plasma samples from nesting females tested positive for brevetoxin (reported as ng brevetoxin-3[PbTx-3] equivalents [eq]/mL) exposure (2.1-26.7ng PbTx-3eq/mL). Additionally, 100% of livers (1.4-13.3ng PbTx-3eq/mL) and yolk sacs (1.7-6.6ng PbTx-3eq/mL) from dead-in-nest hatchlings and 70% of eggs (<1.0-24.4ng PbTx-3eq/mL) tested positive for brevetoxin exposure with the ELISA. We found that plasma brevetoxin concentrations determined by an ELISA in nesting females positively correlated with gamma-globulins, indicating a potential for immunomodulation as a result of brevetoxin exposure. While the sample sizes were small, we also found that plasma brevetoxin concentrations determined by an ELISA in nesting females significantly correlated with liver brevetoxin concentrations of dead-in-nest hatchlings and that brevetoxins could be related to a decreased reproductive success in this species. This study suggests that brevetoxins can still elicit negative effects on marine life long after a bloom has dissipated. These results improve our understanding of maternal transfer and sublethal effects of brevetoxin exposure in marine turtles.

Mercury and selenium ingestion rates of Atlantic leatherback sea turtles (Dermochelys coriacea): a cause for concern in this species?

Bodily accumulation of certain toxic elements can cause physiologic harm to marine organisms and be detrimental to their health and survival. The leatherback sea turtle (Dermochelys coriacea) is a broadly distributed marine reptile capable of consuming hundreds of kilograms of gelatinous zooplankton each day. Little is known about toxicants present in these prey items. Specifically, mercury is a known neurotoxin with no known essential function, while selenium detoxifies bodily mercury, but can be toxic at elevated concentrations. I collected 121 leatherback prey items (i.e., gelatinous zooplankton) from known leatherback foraging grounds and sampled the esophagus and stomach contents of stranded turtles. All samples were analyzed for total mercury and selenium. Additionally, two prey items and three liver samples were analyzed for methylmercury, the most toxic form of the element. Total mercury concentrations in prey items ranged from 0.2 to 17 ppb, while selenium concentrations ranged from <10 to 616 ppb; methylmercury concentrations in liver ranged from 25 to 236 ppb. Prey items had methylmercury concentrations below the limits of detection (<0.4 ppb). Hazard quotients and exposure rates indicate that leatherbacks of all life stages may be at risk for selenium toxicity. For endangered species like the leatherback, continued anthropogenic deposition of mercury and selenium into the environment is concerning, especially since bodily mercury and selenium concentrations increase as organisms age. Because leatherbacks are long-lived and have large daily prey consumption rates, mercury and selenium loads may increase to physiologically harmful levels in this imperiled species.

Essential, trace and toxic element concentrations in the liver of the world's largest bony fish, the ocean sunfish (Mola mola)

No studies document essential (calcium, magnesium, phosphorus, potassium, sodium), trace (barium, boron, chromium, cobalt, copper, iron, manganese, molybdenum, selenium, zinc) or toxic element (antimony, arsenic, cadmium, lead, mercury, thallium) concentrations in any members of the family Molidae, including the world's largest bony fish, the ocean sunfish (Mola mola). Here, we analyzed 21 elements in the liver of one M. mola. These values were compared to liver concentrations in multiple species with spatial and dietary overlap. Concentrations of calcium (3339 ppm wet weight) and iron (2311 ppm wet weight) were extremely elevated in comparison to a number of other fish species, indicating that calcium and/or iron toxicity may have occurred in this animal. Concentrations of toxic elements were generally low, with the exception of cadmium (3.5 ppm). This study represents the first report of essential, trace and toxic elements in this species.

Seasonal trends in nesting leatherback turtle (Dermochelys coriacea) serum proteins further verify capital breeding hypothesis

Serum protein concentrations provide insight into the nutritional and immune status of organisms. It has been suggested that some marine turtles are capital breeders that fast during the nesting season. In this study, we documented serum proteins in neophyte and remigrant nesting leatherback sea turtles (Dermochelys coriacea). This allowed us to establish trends across the nesting season to determine whether these physiological parameters indicate if leatherbacks forage or fast while on nesting grounds. Using the biuret method and agarose gel electrophoresis, total serum protein (median = 5.0 g/dl) and protein fractions were quantified and include pre-albumin (median = 0.0 g/dl), albumin (median = 1.81 g/dl), α1-globulin (median = 0.90 g/dl), α2-globulin (median = 0.74 g/dl), total α-globulin (median = 1.64 g/dl), β-globulin (median = 0.56 g/dl), γ-globulin (median = 0.81 g/dl) and total globulin (median = 3.12 g/dl). The albumin:globulin ratio (median = 0.59) was also calculated. Confidence intervals (90%) were used to establish reference intervals. Total protein, albumin and total globulin concentrations declined in successive nesting events. Protein fractions declined at less significant rates or remained relatively constant during the nesting season. Here, we show that leatherbacks are most likely fasting during the nesting season. A minimal threshold of total serum protein concentrations of around 3.5-4.5 g/dl may physiologically signal the end of the season's nesting for individual leatherbacks. The results presented here lend further insight into the interaction between reproduction, fasting and energy reserves and will potentially improve the conservation and management of this imperiled species.

Mercury and selenium concentrations in leatherback sea turtles (Dermochelys coriacea): population comparisons, implications for reproductive success, hazard quotients and directions for future research

Leatherback sea turtles (Dermochelys coriacea) are long-distance migrants that travel thousands of km from foraging grounds to breeding and nesting grounds. These extensive journeys are fueled by ingestion of an estimated 300-400 kg of prey/d and likely result in exposure to high concentrations of environmental toxicants (e.g., mercury compounds). Increased bodily concentrations of mercury and its compounds in nesting female turtles may have detrimental effects on reproductive success. Leatherbacks have relatively low reproductive success compared with other sea turtles (global average hatching success ~50-60%). To assess toxicants and necessary nutrients as factors affecting leatherback turtle reproductive success at Sandy Point National Wildlife Refuge (SPNWR), St. Croix, U.S. Virgin Islands, we collected blood from nesting female leatherbacks and tissues from their hatchlings (blood from live turtles, liver and yolk sac from dead turtles). We compared the concentrations in those tissues to hatching and emergence success. We found that on SPNWR, hatching and emergence success were more closely related to seasonal factors than to total mercury and selenium concentrations in both nesting females and hatchlings. Selenium concentrations of nesting females were positively correlated with those of their hatchlings. Mercury and selenium in the liver of hatchlings were positively correlated with one another. Turtles with greater remigration intervals tended to have higher blood selenium concentrations, suggesting that selenium accumulates in leatherbacks through time. Through hazard quotients, we found evidence that selenium may be at or above concentrations that may cause physiologic harm to hatchlings. We also found evidence that population level differences exist for these trace elements. The concentrations of mercury and selenium established in this manuscript form a baseline for future toxicant studies.

Maternal health status correlates with nest success of leatherback sea turtles (Dermochelys coriacea) from Florida

Of the seven sea turtle species, the critically endangered leatherback sea turtle (Dermochelys coriacea) exhibits the lowest and most variable nest success (i.e., hatching success and emergence success) for reasons that remain largely unknown. In an attempt to identify or rule out causes of low reproductive success in this species, we established the largest sample size (n = 60-70 for most values) of baseline blood parameters (protein electrophoresis, hematology, plasma biochemistry) for this species to date. Hematologic, protein electrophoretic and biochemical values are important tools that can provide information regarding the physiological condition of an individual and population health as a whole. It has been proposed that the health of nesting individuals affects their reproductive output. In order to establish correlations with low reproductive success in leatherback sea turtles from Florida, we compared maternal health indices to hatching success and emergence success of their nests. As expected, hatching success (median = 57.4%) and emergence success (median = 49.1%) in Floridian leatherbacks were low during the study period (2007-2008 nesting seasons), a trend common in most nesting leatherback populations (average global hatching success = ∼50%). One protein electrophoretic value (gamma globulin protein) and one hematologic value (red blood cell count) significantly correlated with hatching success and emergence success. Several maternal biochemical parameters correlated with hatching success and/or emergence success including alkaline phosphatase activity, blood urea nitrogen, calcium, calcium:phosphorus ratio, carbon dioxide, cholesterol, creatinine, and phosphorus. Our results suggest that in leatherbacks, physiological parameters correlate with hatching success and emergence success of their nests. We conclude that long-term and comparative studies are needed to determine if certain individuals produce nests with lower hatching success and emergence success than others, and if those individuals with evidence of chronic suboptimal health have lower reproductive success.